On the origin of the anuran body-form (Amphibia: Anura)

To explain the typical form of the anuran body, the following hypothesis is proposed: The ancestors of Anura, Urodela and Gymnophiona, having probably much in common, were potential competitors, so they each had to develop in a different ecological direction: Gymnophiona in the soil, Urodela on the surface of the soil specializing in the capture of slow moving prey and the Anura on the surface of the soil in the hunting of swift moving prey. Presumably the ancestors of the anurans were slow animals themselves and had to wait hiding until prey passed by. Also, to protect the body against dehydration it was necessary to dig into the soil and — because of the need to catch swift moving prey — to dig backwards, so that the head remained free. In the following discussion several characteristics of recent anurans and of probable ancestral anurans are examined in the light of this hypothesis.